Forced air heater

ABSTRACT

A forced air heater having a pair of fuel burners supplying heat to a plenum chamber with a fan for providing a flow of air through the plenum chamber. Gaseous fuel supplied to the burners from a high pressure fuel containers drives a pneumatic motor which in turn drives the fan. The fuel leaving the motor output ports is supplied to the burners.

United States Patent [191 Wilkinson [451 Dec. 25, 1973 FORCED AIR HEATER [76] Inventor: David B. Wilkinson, 1723 Fernmont Dr., New Carlisle, Ohio 45344 22 Filed: Feb. 1, 1973 21 Appl. No.: 328,823

2,595,773 5/1952 Davis 432/222 FOREIGN PATENTS OR APPLICATIONS 595,973 12/1947 Great Britain 416/171 Primary Examiner.lohn J. Camby Attorney-Harry A Herbert, Jr. et a1.

[5 7 ABSTRACT A forced air heater having a pair of fuel burners supplying heat to a plenum chamber with a fan for providing a flow of air through the plenum chamber. Gaseous fuel supplied to the burners from a high pressure fuel containers drives a pneumatic motor which in turn drives the fan. The fuel leaving the motor output ports is supplied to the burners.

7 Claims, 5 Drawing Figures sum 1 or 4 PATENTEB DEC 2 5 I975 FORCED AIR HEATER BACKGROUND OF THE INVENTION Devices, which can be used for warming equipment, are needed for use in areas where electrical power is not available. While many small portable heaters are available, there are no forced air heaters available which are suitable for this purpose. The presently available forced air heaters usually have a high noise level or are bulky and require an external power source for starting or for driving the fan.

Some large heating installations make use of the heat produced to supply energy for driving fans, such as in the patents to Summer et al, U.S. Pat. No. 1,769,194, which uses'steam produced by heat to supply power for running a fan and Toney, U.S. Pat. No. 3,091,445, which makes use of the jet effect of the burning fuel to drive a fan. Other types of systems which use power obtained from heat produced by burning fuel to supply power to drive pumps and fans are Schwartzman, U.S. Pat. No. 3,570,261; Harby, U.S. Pat. No. 2,483,045; and Norton et al, U.S. Pat. No. 3,511,049. These systems however are not for use in a small portable heater.

BRIEF SUMMARY OF THE INVENTION Fuels, such as propane and butane, are stored in containers under high pressure. In some uses for these fuel containers, a pressure reducing device is provided to drop the pressure to a suitable pressure for use. According to this invention, use is made of the fuel supply pressure to drive a fan for a forced air heater. The gaseous fuel from the bottle is used to drive a pneumatic motor which in turn drives a fan. The fuel exhausted from the motor is burned in one or more burners, such as Bunsen type burners, to provide heated air which is circulated by the fan.

IN THE DRAWING FIG. 1 is an end elevational view of a forced air heater according to the invention.

FIG. 2 is a rightside view of the device of FIG. 1.

FIG. 3 is a left side view of the device'of FIG. 1.

FIG. 4 is a sectional view of the plenum chamber for the device of FIG. 1 along the line 4-4.

FIG. 5 is a schematic view of the pneumatic motor for the device of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Reference is now made to FIGS. 1 and 2 of the drawing which show a heater having a pair of burners 12 7 connected to a plenum chamber 14. A gas, such as propane, is stored under pressure in a fuel supply container 16. The gas from the supply 16 is fed to a pneumatic motor 18, which drives a fan l9,positioned at one end of plenum chamber 14. A stand tube 20 may be connected to the fuel supply line adjacent the motor input to collect any liquid fuel that may be present and to provide a pressure buffer for the motor. The fuel from the output of the motor is supplied to the jets 21 of burners 12 through supplyline 22 and connector 24. The burner is started by means of a standard piezoelectric starter unit 25 which supplies a spark between probe 27 and flame arrester screen 28, shown in FIG. 4. A flame holder 29 shields the flame from the fan air. An adjustable closure member 30 may be adjusted to set the desired back pressure for burners 12. The piezoelectric starter used is a push-to-lite, impact igniter P/N 365,245 produced by Vernitron.

The pneumatic motor is a conventional pneumatic motor which is normally operated with a ball and plunger type valve. The crank housing 31, piston 32 within cylinder 33, crank mechanism 34 and outlet port system 36 are the same as in the prior art. The valve system has been modified, as shown in FIG. 5, to make the motor suitable for slow speed operation.

A valve member 40 with a projecting pin 42 secured thereto rests in a valve seat 44 and is held closed by gas supply pressure. The piston 32 has a spring member 46 secured to the top thereof. The pressure on the top of valve 40 holds the valve closed against the spring 46 until the spring bottoms out. The valve is then opened. The spring force is sufficient to hold the valve open, however, so that it remains open during part of the pressure stroke of the piston. The delay then permits a sufficient gas charge to enter the cylinder.

In the operation of the device, the fuel container valve 48 is opened to permit a flow of gas to the motor 18 to start the fan 19. Since the motor can run in either direction, positioning marks 49 may be provided to position the piston so that the fan will run in the right direction or the fan can be started by hand in the right direction. The piezoelectric starter 25 is then operated to provide a spark between probe 27 and screen 28, which ignites the fuel air mixture from burners 12. The fan then circulates the hot air and fuel products mixture in plenum chamber 14.

While the fuel products are shown as mixing with the air in the plenum chamber, a heat exchanger could be provided within the plenum chamber so as to provide clean air out of the plenum chamber.

There is thus provided a low cost, low noise level forced air heater which makes the use of an external power source, for driving the fan, unnecessary.

. I claim: a

l. A forced air heater, comprising: a plenum chamher, at least one fuel burner for supplying heat to said plenum chamber, a fan adapted to force air through said plenum chamber, means for storing fuel under pressure, means for supplying fuel from said fuel storing means to said at least one burner, a pneumatic motor connected in said fuel supply means whereby the fuel, from the fuel storage means passes through the motor to drive the motor before being supplied to said at least one burner, said motor being connected to said fan to thereby drive the fan to force air through the pienum chamber.

2. The device as recited in claim 1 including a piezoelectric starter for igniting the at least one burner.

3. The device as recited in claim 2 including a flame holder means within said plenum chamber for shielding the burner flame from the fan.

4. The device as recited in claim 3 including means for controlling the back pressure of said at least one burner.

the gas pressure of the fuel storing means only after the spring bottoms on the piston and to hold the valve open by the action of the spring for a portion of the pressure stroke of the piston.

7. The device as recited in claim 6 including, means adjacent said valve on the side remote from said piston for limiting the travel of said valve. 

1. A forced air heater, comprising: a plenum chamber, at least one fuel burner for supplying heat to said plenum chamber, a fan adapted to force air through said plenum chamber, means for storing fuel under pressure, means for supplying fuel from said fuel storing means to said at least one burner, a pneumatic motor connected in said fuel supply means whereby the fuel, from the fuel storage means passes through the motor to drive the motor before being supplied to said at least one burner, said motor being connected to said fan to thereby drive the fan to force air through the plenum chamber.
 2. The device as recited in claim 1 including a piezoelectric starter for igniting the at least one burner.
 3. The device as recited in claim 2 including a flame holder means within said plenum chamber for shielding the burner flame from the fan.
 4. The device as recited in claim 3 including means for controlling the back pressure of said at least one burner.
 5. The device as recited in claim 1 wherein a stand pipe is connected to the fuel supplying means adjacent the input to said motor to collect any liquid fuel present.
 6. The device as recited in claim 1 wherein said pneumatic motor has in combination with a piston moving in a cylinder and a crank mechanism, for driving said fan, connected to the piston with outlet ports for removing gas from the cylinder; a valving system for intermittently supplying gaseous fuel from the fuel supply to said cylinder to provide a pressure stroke for the piston, comprising: a valve seat at the end of the cylinder remote from said crank mechanism; a valve, adapted to engage the valve seat to close the valve; a spring member secured to said piston on the side adjacent said valve; a pin on said valve projecting toward said piston adapted to engage said spring to open the valve against the gas pressure of the fuel storing means only after the spring bottoms on the piston and to hold the valve open by the action of the spring for a portion of the pressure stroke of the piston.
 7. ThE device as recited in claim 6 including, means adjacent said valve on the side remote from said piston for limiting the travel of said valve. 